A rotating electric motor is one example of a rotating electrical machine. The efficiency in a rotating electric motor has improved significantly because a synchronous electric motor having a rotor equipped with a permanent magnet is used.
However, it is desirable that the efficiency be further improved. A cause of decreased efficiency in a rotating electrical machine is iron loss in the stator core of the stator used in a rotating electrical machine. It is desirable that the iron loss should be reduced to provide a rotating electrical machine which is highly efficient.
For example, technique for reducing iron loss is described in patent document 1. The technique disclosed therein is technique that prevents the increase in iron loss generated due to the stress applied to a stator core as the result of the stator core being inserted into a housing by pressure; that is, the technique suppresses the generation of stress by creating a gap between the stator core and the housing, thereby preventing the increase in iron loss.
Furthermore, documents which describe the etching of a magnetic body include patent document 2, patent document 3, patent document 4, patent document 5, patent document 6, patent document 7, patent document 8, patent document 9, and patent document 10.
[Patent document 1] Japanese Patent Laid-open Publication No. 2004-201428
[Patent document 2] Japanese Patent Laid-open Publication No. 2000-197320
[Patent document 3] Japanese Patent Laid-open Publication No. 2004-281737
[Patent document 4] Japanese Patent Laid-open Publication No. 2005-300211
[Patent document 5] Japanese Patent Laid-open Publication No. 2002-078296
[Patent document 6] Japanese Patent Laid-open Publication No. 2005-160231
[Patent document 7] Japanese Patent Laid-open Publication No. Hei 11-155263
[Patent document 8] Japanese Patent Laid-open Publication No. Hei 09-117083
[Patent document 9] Japanese Patent Laid-open Publication No. Hei 05-284697
[Patent document 10] Japanese Patent Laid-open Publication No. Hei 09-275007